BÀI 1 TÌM X ,BIẾT a.X.3/7+4/7=-2/7 b. X .(3/7- -4/7) =-2/7 c.( X – 3/-7).4/7=-2/7 BÀI 2 SO SÁNH A,-4/3 VÀ 11/-5 B,23/48 VÀ 19/36 C. 56/51 VÀ 66/61 LÀ

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1. $Bài\ 1 : \\a.x.\dfrac{3}{7}+\dfrac{4}{7}=\dfrac{-2}{7} \\⇔x.\dfrac{3}{7}=\dfrac{-2}{7}-\dfrac{4}{7} \\⇔x.\dfrac{3}{7}=\dfrac{-6}{7} \\⇔x=\dfrac{-6}{7}:\dfrac{3}{7} \\⇔x=-2 \\b.x.\bigg(\dfrac{3}{7}-\dfrac{-4}{7}\bigg)=\dfrac{-2}{7} \\⇔x.1=\dfrac{-2}{7} \\⇔x=\dfrac{-2}{7} \\c.\bigg(x-\dfrac{3}{-7}\bigg).\dfrac{4}{7}=\dfrac{-2}{7} \\⇔x-\dfrac{-3}{7}=\dfrac{-2}{7}:\dfrac{4}{7} \\⇔x-\dfrac{-3}{7}=\dfrac{-1}{2} \\⇔x=\dfrac{-1}{2}+\dfrac{-3}{7} \\⇔x=\dfrac{-13}{14} \\Bài\ 2 : \\a.\dfrac{-4}{3}=\dfrac{-4.5}{3.5}=\dfrac{-20}{15} \\\dfrac{11}{-5}=\dfrac{-11.3}{5.3}=\dfrac{-33}{15} \\Ta\ có : \\\dfrac{-20}{15}>\dfrac{-33}{15} \\⇒\dfrac{-4}{3}>\dfrac{11}{-5} \\b.\dfrac{23}{48}=\dfrac{23.3}{48.3}=\dfrac{69}{144} \\\dfrac{19}{36}=\dfrac{19,4}{36.4}=\dfrac{76}{144} \\Ta\ có : \\\dfrac{69}{144}<\dfrac{76}{144} \\⇒\dfrac{23}{48}<\dfrac{19}{36} \\c.Ta\ có : \\\dfrac{56}{51}-1=\dfrac{5}{51} \\\dfrac{66}{61}-1=\dfrac{5}{61} \\Ta\ có : \\\dfrac{5}{51}>\dfrac{5}{61} \\⇒\dfrac{56}{51}>\dfrac{66}{61}$

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2. Bài 1:

   a,  x.$\frac{3}{7}$ + $\frac{4}{7}$ = $\frac{-2}{7}$

        x.$\frac{3}{7} = $$\frac{-2}{7}$$ – $$\frac{4}{7}$

        x.$\frac{3}{7}$= $\frac{-6}{7}$

        x = $\frac{-6}{7}$ : $\frac{3}{7}$

        x = -2

   b,  x.($\frac{3}{7}$ – $\frac{-4}{7}$) = $\frac{-2}{7}$

        x . 1 = $\frac{-2}{7}$

        x = $\frac{-2}{7}$

   c,  (x – $\frac{3}{-7}$).$\frac{4}{7}$ = $\frac{-2}{7}$

        (x – $\frac{3}{-7}$) = $\frac{-2}{7}$ : $\frac{4}{7}$

         (x – $\frac{3}{-7}$) = $\frac{-1}{2}$

         x – $\frac{3}{-7}$ = $\frac{-1}{2}$ + $\frac{3}{-7}$  

         x = $\frac{-13}{14}$   

   Bài 2:

   a,  $\frac{-4}{3}$ và $\frac{11}{-5}$ 

   $\frac{-4}{3}$ = $\frac{-20}{15}$; $\frac{11}{-5}$ = $\frac{-33}{15}$

   ⇒ $\frac{-4}{3}$ > $\frac{11}{-5}$ 

   b,  $\frac{23}{48}$ và $\frac{19}{36}$   

      $\frac{23}{48}$ = $\frac{69}{144}$; $\frac{19}{36}$ = $\frac{76}{144}$

   ⇒ $\frac{23}{48}$ < $\frac{19}{36}$   

   c, $\frac{56}{51}$ và $\frac{66}{61}$

       $\frac{56}{51}$ = $\frac{3416}{3111}$; $\frac{66}{61}$ = $\frac{3366}{3111}$

   ⇒ $\frac{56}{51}$ < $\frac{66}{61}$

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